﻿#include<iostream>
using namespace std;
int main() {
	char a;

	int b{};
	cout << b << endl;

linput:
	cout << "写" << endl;
	cin >> a;
	if (a > 64 && a < 91) {
		a += 32;
		cout << a;
		goto linput;
	}
	else {
		cout << "错误！" << endl;
		goto linput;
	}
}